Driver assistance systems are known from practice, which assist a driver of a motor vehicle in maneuvering, in parking and/or in leaving a parking space and which include a sensor system that detects the surroundings of the motor vehicle and that may have ultrasonic sensors for this purpose. In particular, systems are known, which include a parking space measuring device of a motor vehicle and which use this to assist the driver when parking into a parking space.
For example, a parking assistant is known from German Published Patent Application No. 198 09 416, which assists the driver when parallel parking by backing into a parking space between two vehicles parked at the edge of a road. In the method implemented in this system, a potential parking space is approached and measured by the sensors situated on the motor vehicle. Subsequently, an ascertainment is made as a function of stored reference values as to whether the parking space is sufficiently large for a parking operation of the motor vehicle. If this is the case, then a parking strategy is calculated as a function of the size of the parking space and is communicated to the driver of the motor vehicle. The driver may then follow the proposed parking strategy so as to avoid long and/or unsuccessful parking operations.
It is fundamentally important whether the motor vehicle at the beginning of a parking operation is oriented parallel to the alignment of the motor vehicles adjoining the parking space or parallel to the adjoining curb. If this is not given, then the specification of a parking strategy in the latter case includes a correction of the alignment, i.e. of the yaw angle, between the longitudinal axis of the vehicle and the curb. Following the conclusion of the parking operation, the vehicle is aligned parallel to the curb, i.e. the yaw angle is 0°.
A provision was made to calculate a parking path using so-called clothoids. The yaw angle is corrected by shortening or lengthening the first circular arc that must be followed when parking and that has a so-called starting clothoid assigned to it. If the surfaces below the steering angle characteristics represented by the starting clothoid and a so-called turning clothoid are of equal size, then it is possible to speak of a so-called parallel parking process since in this case the integration of the steering angle characteristics states the yaw angle. If now the first circular arc that must be followed is changed, then the vehicle may be parked parallel to the curb even if the initial yaw angle deviates from 0°.
Furthermore, there is the problem in a parking operation that after passing the parking space the motor vehicle is usually oriented obliquely with respect to the curb since it is often difficult for the driver to move the motor vehicle parallel with respect to the curb. This oblique position must then be corrected during the parking operation. When varying the first circular arc that must be followed to correct the initial yaw angle, i.e. when changing the arc length of the so-called trajectory, the motor vehicle may possibly collide with motor vehicles adjoining the parking space. Thus, to avoid such collisions, a very costly calculation strategy would have to be employed to take into account the initial yaw angle.